The present invention relates generally to shifters for automotive transmissions and, more particularly, is directed to a drop-in type automotive transmission shifter which is spring biased into the neutral position with one or more flat springs.
Drop-in type shifters are well-known in the prior art. These shifters normally comprise a shift stick means for pivotally mounting the shift stick about a base, and a gear actuating lever which extends into the transmission for changing the drive ratio of the transmission when the shift stick is manually pivoted. Often the means for pivotally mounting the shift stick comprises a ball and socket connection. The shifter is normally secured to the top of a transmission with bolts entering through the base of the shifter. The base is usually bolted over an aperture in the top of the transmission and the shift lever extends downwardly from the base through the aperture into the transmission. Hence, these types of shifters have been referred to as drop-in type shifters.
It has often been considered desirable to spring bias an automotive transmission shifter into a neutral position or neutral plane. In the case of a conventional manual automotive transmission having a H-shaped shift pattern implemented with a shift stick which is pivotable about first and second orthogonal axes, it has also been thought to be desirable to provide a differential spring bias which may, for example, be used to inhibit positioning the shifter in one or more gear positions such as the reverse gear position.
One such shifter is disclosed in U.S. Pat. No. 4,569,245 to Feldt et al. In U.S. Pat. No. 4,569,245 several pivotable drop-in shifters are disclosed, each having one or more washer-like springs for biasing a shift lever into a neutral position. The washer-like springs are preformed into a free-state bowed or bent condition and then placed in a compressed condition in the shifter in a manner such that a rocking shaft extended through the shifter stick engages the washer-like springs to bias the shifter stick to the neutral position. In particular, the washer-like springs are compressed between the rocking shaft and a housing plate so that the washer-like springs engage the ends of the rocking shaft to bias the rocking shaft and thus the shifter stick moves towards the neutral position. Consistent shape is important to this arrangement so that the springs give a predictable biasing force. However, spring steel is difficult to preform into a consistent shape due to the spring steel's natural resiliency and its tendency not to predictably permanently deform. Further, the lack of consistent shape tends to make use of multiple stacked or interleaved springs less desirable since the inconsistent shape tends to cause non-uniform and unpredictable biasing forces. Also, when installed the shaped spring requires an accurate placement of the springs within the housing to provide the proper orientation necessary to provide the predictable biasing force. Accordingly, inefficiencies during assembly are caused in addition to the possibilities of inaccurate biasing forces being created.
Thus, an improved shifter solving the aforementioned problems is desired.